Building management systems may for example be used to supervise and control the indoor climate of a building. Such systems may comprise several control devices which are connected in a network. The control devices may receive measurement data from sensors. Further, a user may input reference values (i.e., set point values) to the control devices, for example in the form of a desired temperature.
Such systems may also comprise portable sensor devices which measure parameters, such as temperature. The portable sensor devices are preferably worn by or placed in the vicinity of an occupant of the building and hence measure parameters in the vicinity of the occupant. Further, the occupant may input and store personal settings, such as desired climate parameters in the portable sensor devices.
A general problem with portable sensor devices is that their energy storage is limited since they typically are self-powered or driven by batteries.
US2010/0163633 discloses a control system for a heating, ventilating, and air-conditioning (HVAC) system. The disclosed system comprises controllers in the form of distributed nodes connected in a wireless network. The system further comprises a portable remote control unit by which a user, via a display and a keyboard, may instruct the control system to change a parameter such as a desired temperature in the region where the user is located. The remote control unit may also be docketed with a thermostat. If so, the remote control unit may receive power from the thermostat circuit and communicate with the nodes at a regular two-minute time interval. If not docked, these time intervals are much further spaced in time in order for the remote control unit to conserve power and extend battery life of the remote control unit. A user may bring the portable remote control unit along inside of a building and set a desired temperature as he/she enters a room by pointing the portable remote control unit to one of the controllers of the temperature. Further, in order to indicate that the room is occupied he/she may press a button on the remote control unit.
A drawback with this approach is that the user manually has to perform an action when he/she enters a new room in order to, for example, set a desired temperature value or to indicate that he/she has entered the room. There is thus a need for improvements.